CMOS image sensor chips are typically used in mobile devices such as cell phone cameras to capture images (e.g. cell phone camera or video functionality). These image sensors are usually very small and compact, given the limited size and weight requirements for mobile devices. The image sensor chip includes one or more lenses that are used to focus the incoming light onto a light sensor. The light sensor converts the incoming light into electronic signals that represent the image formed by the incoming light.
Lenses are often made of glass or polymer, and are typically made using a molding process. For example, polymer lenses are typically manufactured using molding techniques such as injection molding and transfer molding. Injection molding, for example, involves injecting polymer in a liquid state into a mold cavity. The polymer is then cooled so that it solidifies in the shape of the mold. The polymer is then removed from the mold in the form of a lens.
Molded lenses are easily mass-produced. For example, pluralities of molds are simultaneously injected with the lens material in a fluid state, followed by cooling, resulting in simultaneous formations of lenses. Traditional molding techniques produces lens that are monolithic, such that the optical properties from a single lens are limited. Therefore, for those applications requiring complex optical properties, multiple monolithic lenses of varying configuration can be stacked together. However, stacked monolithic lens configurations can be costly and excessively large in size.
There is a need for an improved lens and manufacturing technique for mass producing the lens that provides diverse optical property performance without adding significant cost or size.